Hybrid drive employing non-volatile semiconductor memory to facilitate refreshing disk
A hybrid drive is disclosed comprising a head actuated over a disk comprising a plurality of data sectors, and a non-volatile semiconductor memory (NVSM). A plurality of refresh zones are defined, wherein each refresh zone comprises a plurality of the data sectors on the disk, and a refresh monitor is maintained for each refresh zone. When a write command is received from a host comprising data and the data is targeted to the NVSM, the data is written to the NVSM. When the data is targeted to a first refresh zone on the disk, and a first refresh monitor has not reached a refresh limit, the data is written to the first refresh zone. When the data is targeted to the first refresh zone on the disk, and the first refresh monitor has reached the refresh limit, the data is written to the NVSM.
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Hybrid drives are conventional disk drives augmented with a non-volatile semiconductor memory (NVSM) such as a flash which helps improve certain aspects of the disk drive. For example, the non-volatile semiconductor memory may store boot data in order to expedite the boot operation of a host computer. Another use of a
NVSM may be to store frequently accessed data and/or non-sequential data for which the access time is typically much shorter than the disk (which suffers from mechanical latency including seek and rotational latency). Other policies may reduce write amplification of the NVSM in order to maximize its longevity, such as storing frequently written data to the disk (or data having a write/read ratio that exceeds a predetermined threshold).
In the embodiment of
The disk 4 shown in the embodiment of
When a refresh monitor reaches a refresh limit indicating that the corresponding refresh zone needs to be refreshed, subsequent write operations targeted to the refresh zone are redirected to the NVSM rather than holding off the host. The NVSM is used to service write commands targeted to the refresh zone until the refresh zone is refreshed and able to service subsequent write commands.
In another embodiment shown in the flow diagram of
In one embodiment, if an LBA corresponding to data stored in the NVSM is overwritten (by a subsequent write operation after refreshing a refresh zone), the new data is written to the refresh zone on the disk and the memory segment of the NVSM is invalidated and eventually erased during a garbage collection operation.
Any suitable control circuitry may be employed to implement the flow diagrams in the embodiments of the present invention, such as any suitable integrated circuit or circuits. For example, the control circuitry may be implemented within a read channel integrated circuit, or in a component separate from the read channel, such as a disk controller and/or NVSM controller, or certain steps described above may be performed by a read channel and others by a disk controller and/or NVSM controller. In one embodiment, the read channel and controllers are implemented as separate integrated circuits, and in an alternative embodiment they are fabricated into a single integrated circuit or system on a chip (SOC). In addition, the control circuitry may include a suitable preamp circuit implemented as a separate integrated circuit, integrated into the read channel or disk controller circuit, or integrated into an SOC.
In one embodiment, the control circuitry comprises a microprocessor executing instructions, the instructions being operable to cause the microprocessor to perform the steps of the flow diagrams described herein. The instructions may be stored in any computer-readable medium. In one embodiment, they may be stored on a non-volatile semiconductor memory external to the microprocessor, or integrated with the microprocessor in a SOC. In another embodiment, the instructions are stored on the disk and read into a volatile semiconductor memory when the hybrid drive is powered on. In yet another embodiment, the control circuitry comprises suitable logic circuitry, such as state machine circuitry.
Claims
1. A hybrid drive comprising:
- a disk comprising a plurality of data sectors;
- a head actuated over the disk;
- a non-volatile semiconductor memory (NVSM); and
- control circuitry operable to: define a plurality of refresh zones, wherein each refresh zone comprises a plurality of the data sectors on the disk; maintain a refresh monitor for each refresh zone; receive a write command from a host comprising data; when the data is targeted to the NVSM, write the data to the NVSM; when the data is targeted to a first refresh zone on the disk, and a first refresh monitor has not reached a refresh limit, write the data to the first refresh zone; and when the data is targeted to the first refresh zone on the disk, and the first refresh monitor has reached the refresh limit, write the data to the NVSM.
2. The hybrid drive as recited in claim 1, wherein the control circuitry is further operable to update the first refresh monitor in connection with writing data to the first refresh zone.
3. The hybrid drive as recited in claim 2, wherein the control circuitry is further operable to update the first refresh monitor over time.
4. The hybrid drive as recited in claim 1, wherein the control circuitry is further operable to write the data to the NVSM when refreshing any one of the refresh zones.
5. The hybrid drive as recited in claim 1, wherein the control circuitry is further operable to flush at least part of the data from the NVSM to the first refresh zone after refreshing the first refresh zone.
6. The hybrid drive as recited in claim 5, wherein the control circuitry is further operable to flush the data least frequently read.
7. The hybrid drive as recited in claim 5, wherein the control circuitry is further operable to flush at least part of the data in connection with executing a wear leveling algorithm for the NVSM.
8. A method of operating a hybrid drive comprising a head actuated over a disk comprising a plurality of data sectors, and a non-volatile semiconductor memory (NVSM), the method comprising:
- defining a plurality of refresh zones, wherein each refresh zone comprises a plurality of the data sectors on the disk;
- maintaining a refresh monitor for each refresh zone;
- receiving a write command from a host comprising data;
- when the data is targeted to the NVSM, writing the data to the NVSM;
- when the data is targeted to a first refresh zone on the disk, and a first refresh monitor has not reached a refresh limit, writing the data to the first refresh zone; and
- when the data is targeted to the first refresh zone on the disk, and the first refresh monitor has reached the refresh limit, writing the data to the NVSM.
9. The method as recited in claim 8, further comprising updating the first refresh monitor in connection with writing data to the first refresh zone.
10. The method as recited in claim 9, further comprising updating the first refresh monitor over time.
11. The method as recited in claim 8, further comprising writing the data to the NVSM when refreshing any one of the refresh zones.
12. The method as recited in claim 8, further comprising flushing at least part of the data from the NVSM to the first refresh zone after refreshing the first refresh zone.
13. The method as recited in claim 12, further comprising flushing the data least frequently read.
14. The method as recited in claim 12, further comprising flushing at least part of the data in connection with executing a wear leveling algorithm for the NVSM.
Type: Grant
Filed: Oct 21, 2010
Date of Patent: Apr 23, 2013
Assignee: Western Digital Technologies, Inc. (Irvine, CA)
Inventor: Chun Sei Tsai (Tustin, CA)
Primary Examiner: Kevin Verbrugge
Application Number: 12/909,555
International Classification: G06F 12/00 (20060101);